Combination of an anti-EDb fibronectin antibody-IL-2 fusion protein, and a molecule binding to B cells, B cell progenitors and/or their cancerous counterpart

ABSTRACT

The present invention relates to a combination of an anti-EDb fibronectin antibody-IL-2 fusion protein, and a molecule binding to B cells, B cell progenitors and/or their cancerous counterpart and uses thereof.

This application claims the benefit of the filing dates of U.S.Provisional Application Ser. No. 61/021,718 filed Jan. 17, 2008, and EPapplication 08075044.1, filed Jan. 17, 2008, which are incorporated byreference herein.

The present invention relates to a combination of an anti-EDbfibronectin antibody-IL-2 fusion protein, and a molecule binding to Bcells, B cell progenitors and/or their cancerous counterpart and usesthereof.

B cell non-Hodgkin lymphoma (B-NHL), a group of histopathologically andclinically distinct malignancies derived from B lymphocyte precursorcells, is the most common group of hematologic malignancies.Accordingly, malignant lymphocytes from B-NHL patients expresscharacteristic B cell markers on their cell surfaces such as CD20, CD 23and others. B-NHL accounts for over 50000 newly diagnosed cases and 5%of cancer-related deaths in the United States each year.

Rituximab (RITUXAN®) is a chimeric monoclonal IgG1 antibody thatdirectly binds to the CD20 cell surface epitope constitutively expressedon the cell surface of malignant and normal B cell populations. By sodoing, rituximab (a) elicits antibody-dependent cellular cytotoxicity(ADCC), (b) induces lymphoma cell death through complement-dependentcytolysis (CDC) and/or complement-dependent cellular cytotoxicity, and(c) directly induces apoptosis following the engagement of CD20 byrituximab. In addition, (d) rituximab possibly has a vaccinal effectimplemented via cross-presentation of lymphoma antigens fromrituximab-killed malignant B cells by antigen-presenting cells andpriming of lymphoma antigen-specific cytotoxic T cells (Selenko et al,2001).

-   -   A) ADCC: This mechanism involves binding of the antibody's Fc        portion to the Fcγ receptors expressed on immune cells with        cytotoxic capabilities such as monocytes, natural killer cells,        and granulocytes, which would then lead to destruction of the        rituximab-bound B cells either by phagocytosis or release of        cytotoxic granules contained in immune effector cells. ADCC is        currently considered to be the major mechanism of action of        rituximab.    -   B) CDC: Since the Fc portion of rituximab binds to complement,        lymphoma cell death can be achieved through CDC. However, recent        findings that rituximab-induced B cell depletion still occurs in        mice genetically deficient of complement factors tempered the        initial enthusiasm for this mechanism of action.    -   C) Induction of apoptosis: In vitro studies have shown that        engagement of CD20 by rituximab triggers a cascade of        intracellular signaling events and selective down-regulation of        antiapoptotic factors. It also translocates CD20 into lipid        rafts and activates caspase via increased calcium mobilization        (Janas et al, 2005). In CLL patients, it was found that        circulating B cells display activation of several caspases and        poly (ADP-ribose) polymerase (PARP) cleavage immediately after        the infusion of rituximab, long before other potential        mechanisms such as ADCC could be triggered in vivo (Byrd et al,        2002).    -   D) Vaccinal effect/T cell response: The clinical findings that        retreatment with rituximab was associated with a longer median        response duration as the first treatment was and that in those        patients who responded to retreatment, the antitumor effect of        rituximab persisted long after the antibody was cleared from the        circulation (Davis et al, 2000) strongly hints to a specific        immunologic mechanism involved.

Treatment with rituximab as a single agent induces significant butmoderate and short-lasting responses in patients with almost everysubtype of B-cell lymphoma. However, its biggest benefit is seen when itis combined with induction chemotherapy regimens (Coiffier, 2006).Combined with standard chemotherapy, in particular with CHOP(cyclophosphamide, vincristine, adriamycin and prednisolone), rituximabat a dose of 375 mg/m² as a 90-min intravenous infusion on day 1 of eachchemotherapy cycle even increases the cure rate of patients with diffuselarge B cell lymphoma (DLBCL) to approximately 52% (Coiffier 2002,update of GELA OS data, ASH 2007) from 38% with chemotherapy alone.

In indolent lymphoma, the addition of rituximab to every inductionchemotherapy combination (FCM, CVP, CHOP, FND) has resulted in asignificant increase in the overall response and complete remissionrates as well as in a delay of the time to disease progression (Marcus,2005; Hiddemann 2005). However, adding rituximab to chemotherapy notalways leads to improved clinical outcomes. In patients with mantle celllymphoma, treatment with CHOP plus rituximab resulted in a similarprogression-free survival and overall survival compared with patients onCHOP therapy alone (Lenz et al, 2005).

In addition to its established role as a treatment to induce remissions(induction therapy) in B-NHL patients, rituximab monotherapy also hasbeen evaluated as a maintenance therapy to consolidate responses orprolong remissions. Under the assumption that 25 mg rituximab/ml is thelowest acceptable serum concentration, a dose of 375 mg/m² rituximabinfused every 3 months was found to be sufficient for rituximabmaintenance therapy in a prospective pharmacokinetic study (Gordan,2005). Although some studies have shown a significant clinical benefitwhen using maintenance rituximab after initial standard chemotherapywith CVP (Hoechster, 2005) or CHOP (Habermann, 2006), it is stillunclear whether rituximab maintenance therapy provides additionalbenefit to those patients in whom it was used as a part of the inductionchemotherapy (e.g. R-CHOP).

Unfortunately and despite the unquestionable clinical effectiveness ofrituximab in combination with chemotherapy (e.g. R-CHOP), the majorityof B-NHL patients still dies eventually of progressive disease. Inaddition, despite being an effective agent in the treatment of B-NHLs,approximately 50% of patients with relapsed/refractory CD20+ follicularlymphomas do not respond to initial treatment with rituximab (innateresistance; McLaughlin et al 1998), and about 60% of prior rituximabresponding patients will not benefit from retreatment with rituximab(acquired resistance; Davis et al, 2000). It is currently unclear,whether these forms of rituximab-resistance are due to an adaptiveproperty of the malignant B cells or to an impaired host's immuneeffector mechanism. Anyway, rituximab resistance represents asignificant barrier to immuno- and immonochemotherapy of B-NHLs in termsof further improved clinical outcome.

Although rituximab/chemotherapy combinations have been analyzed, thereis still a strong and persistent need for further therapy improvements.Two general strategies are currently being pursued: a) engineering novelanti-CD20 antibodies, and b) creating monoclonal antibodies that targetB cell antigens other than CD20. Two categories of new anti-CD20monoclonal antibodies are currently in clinical evaluation: a) anti-CD20antibodies displaying higher affinity than rituximab for the Fc-receptorFcγRIIIa (CD16), and b) anti CD20 antibodies with lower immunogenicity(humanized; Tbl 1). The presumably strongest of these antibodies,GA-101, a humanized anti CD20 antibody with a glyco-engineered Fcportion and a modified elbow hinge results in a 10-100 fold increase inADCC against NHL cell lines. Small phase I/II studies with anti-CD20antibodies with lower immunogenicity show response rates in the order of50% in relapsed B-NHL patients (Coiffier, 2006; Hagenbeek, 2005;Morschhauser, 2005). Monoclonal antibodies targeting surface moleculesother than CD20 in B-NHLs such as lumilixumab (anti-CD23), epratuzumab(anti-CD22), SGN-40 and HCD122 (both anti-CD40), galiximab (anti-CD80),apolizumab (Hu1D10), KRN848, 1D09C3 (all anti-HLA-DR) have shown promisein early clinical trials. Novel anti-CD20 antibodies and antibodiesdirected against non-CD20 B-cell epitopes will have to demonstrate asignificantly superior efficacy over rituximab to be consideredsuccessful, however, early clinical results with the most of theseantibodies indicate incremental benefits, only.

There have been efforts to combine rituximab with unconjugated IL-2(Eisenbeis et al., 2004; Gluck et al., 2004).

However, the results of a recent phase II trial indicated that“rituximab plus rIL-2 combination therapy was safe and generally welltolerated, but responses were low” (Khan et al., 2006, Clin Cancer Res2006; 12(23): 7046-7053). Also, it was found that “rIL-2 expandsFcR-bearing cellular subsets in vivo and enhances in vitro ADCC ofrituxumab”. However, it was concluded by the authors that these findings“did not directly translate into meaningful clinical benefit forpatients with rituxumab-refractory NHL”. Moreover, the authors concludedthat “a better understanding of rituximab's in vivo a mechanism ofaction will likely be required before further advances in favorablymodulating its antitumor activity can be made”.

In addition to cancer indications, anti B cell antibodies an rituximabin particular are being developed for the treatment of autoimmunediseases, including rheumatoid arthritis, Crohn's disease and autoimmunehemolytic anemia. (Assous et al, 2008).

Taking into consideration standard therapies as well as new treatmentoptions currently in clinical development, there is still a strongmedical need for designing more active treatments for B-cell lymphomapatients, which preferentially lead to complete remissions and/or areuseful to treat rituximab-resistant lymphoma. There is also a strongmedical need for providing new medicaments for treating autoimmunedisease, in particular chronic autoimmune diseases.

TABLE 1 Anti-CD20 antibodies CDC (complement- Antibody dependent nameType ADCC cytotoxicity) Direct effects Reference rituximab Chimeric ++++ + Cragg et al IgG1 Ocrelizumab Humanized +++ +/− + Vugmeyster IgG1 etal PRO131921 Engineered ++++ ++ + ocrelizumab Veltuzumab Humanized ++++ + Stein et al IgG1 Ofatumumab Human IgG1 ++ ++++ + Hagenbeck et alAME-133 Humanized ++++ ++ ++ Weiner et al IgG1 GA-101 Humanized +++++ −++++ Umana et al IgG1

TABLE 2 Selected anti-B cell antibodies in clinical trials withnon-Hodgkin lymphoma patients Objective response Antibody rate, (%, NHLname Type DLT entity)/clinical data Reference Rituximab Chimeric None48, relapsed FL McLaughlin et al IgG1 Epratuzumab Humanized None 43,relapsed FL Leonard et al (a) (anti-CD22) IgG1 Epratuzumab + CombinationNone 67, relapsed FL Leonard et al (b) rituximab Lumiliximab None Activein CLL when (anti-CD23) combines w/chemo Galiximab Humanized None 11,relapsed FL Czuczman et al (anti-CD80) IgG1 Galiximab + Combination None66, relapsed FL Leonard et al (c) rituximab SGN-40, Humanized Cytokinerelease 0 Advani et al (anti-CD40) IgG1 HCD122 Ongoing Phase I ongoing(anti-CD40) Anti-CD22- Humanized Thrombocytopenia 69, relapsed FL Fayadet al calicheamicin IgG4 (CMC-544) BL22 (anti- Hemolytic Responses inhairy CD22 uraemic syndrome cell leukemia coupled to pseudomonasexotoxin

The extra domain B (EDB) of fibronectin is one of the best-characterizedmarkers of angiogenesis described so far (Zardi et al., Embo J. 1987;6:2337-2342; Kaspar et al., Int J Cancer. 2006; 118:1331-1339). This91-amino acid type III homology domain can be inserted into thefibronectin molecule during active tissue remodeling by a mechanism ofalternative splicing (Zardi et al., supra). EDB is essentiallyundetectable in healthy adult tissues but is highly abundant in thevasculature of many aggressive solid tumors. The tumor-targeting abilityof the high-affinity human antibody L19 (Pini et al., J Biol. Chem.1998; 273:21769-21776), specific to EDB, has been well established bothin animal models of cancer (Tarli et al., Blood. 1999; 94:192-198; Borsiet al., Int J. Cancer. 2002; 102:75-85; Berndorff et al., J Nucl Med.2006; 47:1707-1716; Berndorff et al., Clin Cancer Res. 2005;11:7053s-7063s; Demartis et al., Eur J Nucl Med. 2001; 28:534-53) and inpatients with solid tumors (Santimaria et al., Clin Cancer Res. 2003;9:571-579). Recently, ED-B expression was also found in the majority oflymphoma-infiltrated tissue samples from various Non-Hodghkin lymphomapatients (Sauer et al., 2006).

Based on current knowledge about antibody-based cancer therapies inparticular when combined with rIL-2 or similar cytokines, it wassurprising to find in combination therapy experiments in mice, that thecombination of rituximab with the L19-IL2 fusion induced completeeradications of established Ramos lymphomas in 4 of 5 mice in the highdose L19-IL2 group (L19-IL2_(high dose) vs. saline: P<0.00001), with 3of 4 CRs (complete remessions) already being achieved after 3injections. In fact, the immunocytokine was remarkably more potent thanthe corresponding equimolar amount of unconjugated rIL-2 in combinationwith rituximab (L19-IL2_(high dose) vs. rIL-2_(high dose): P<0.001).Notably, even L19-IL2 at the lowest dose level combined with rituximabstill displayed an excellent therapeutic activity (L19-IL2_(low dose)vs. saline: P<0.00001; L19-IL2_(low dose) vs. rIL-2_(low dose):P<0.00001), inducing CRs in 4 of 5 cases after 4 cycles of therapy,whereas even a three-fold higher dose of the non-targeted cytokinecombined with rituximab was only able to retard tumor growth(L19-IL2_(low dose) vs. rIL-2_(high dose): P<0.001).

Therefore, in one embodiment, the invention relates to a combinationcomprising at least

-   -   (i) a fusion protein comprising an antibody-part specifically        recognising ED_(b)-fibronectin and an Interleukin-2 part and    -   (ii) a molecule binding to B cells, B cell progenitors and/or        their cancerous counterpart.

In a preferred embodiment, the molecule binding to B cells, B cellprogenitors and/or their cancerous counterpart is specifically bindingto CD20, CD23, CD22, CD40, CD80, HLA-DR or Hu1D10.

In a preferred embodiment the molecule binding to B cells, B cellprogenitors and/or their cancerous counterpart is selected from anantibody, antibody fragment or antibody mimetic.

Preferred is a molecule specifically binding to CD20, CD23, CD22, CD40or CD80 which is a full-length antibody or antibody fragment, or afusion protein thereof.

In a particularly preferred embodiment, the antibody or antibodyfragment, or fusion protein thereof is specifically binding to CD20.

In one embodiment, the invention relates to a combination comprising atleast

-   -   (i) a fusion protein comprising an antibody-part specifically        recognising ED_(b)-fibronectin and an Interleukin-2 part and    -   (ii) a molecule specifically binding to CD20.

In a further embodiment, the invention relates to a combinationcomprising at least

-   -   (i) a fusion protein comprising an antibody-part specifically        recognising ED_(b)-fibronectin and an Interleukin-2 part and    -   (ii) a molecule specifically binding to cells expressing CD20.

In a particularly preferred embodiment, the molecule specificallybinding to cells expressing CD20 and/or specifically binding to CD20 isan antibody or antibody fragment specifically binding to CD20.

In a preferred embodiment, the antibody-part of (i) specifically bindsto the EDb-domain of fibronectin (FN). Such antibodies are known in theprior art and are e.g. described in WO 97/45544.

In another embodiment, the antibody specifically recognizingEDb-fibronectin binds to a cryptic epitope. An example for such antibodyis the BC-1 antibody.

Preferably, such antibody which binds to the EDb-domain of fibronectinexhibits a high affinity for the EDb-domain of FN, in particular, theantibody binds to the EDb fibronectin domain with nanomolar orsubnanomolar affinity. Such antibodies are known in the prior art andare e.g. described in WO99/58570.

In particular preferred is the L19 antibody.

The antibody part specifically recognizing EDb fibronectin, inparticular the L19 antibody, can be employed in various antibodyformats. Preferred antibody formats are full IgG, Fab, (Fab′)₂, scFv,diabody, minibody or small immunoprotein (SIP) format. Especiallypreferred are the full IgG, scFv and SIP format for the L19 antibody.Most preferred is the L19 antibody in the scFv format. Severalimmunoprotein formats are known in the prior art, e.g. based on the CH3domain or the ε_(s2)-CH4 domain of IgE. The preferred SIP format for L19based on the ε_(s2)-CH4 domain of IgE and L19 in full IgG format are forexample described in WO03/076469.

In a further preferred embodiment, the antibody-part contains at leastone CDR sequence of the L19 antibody.

In an especially preferred embodiment, the antibody-part comprises theCDR sequences of the L19 antibody, in particular it comprises thesequences according to SEQ ID no. 6 to 11.

In a further preferred embodiment, the antibody-part comprises the VLand VH chain of the L19 antibody. In a preferred embodiment, itcomprises least one VH chain according to SEQ ID No. 1 or at least oneVL chain according to SEQ ID No. 2. In an especially preferredembodiment, it comprises least one VH chain according to SEQ ID No. 1and at least one VL chain according to SEQ ID No. 2.

In a further preferred embodiment, the antibody-part comprises one VHchain according to SEQ ID No. 1 and one VL chain according to SEQ ID No.2. In a further preferred embodiment, the antibody-part comprises two VHchains according to SEQ ID No. 1 and two VL chains according to SEQ IDNo. 2.

In a further preferred embodiment, the VH and the VL chains areconnected by an antibody linker.

In a preferred embodiment, the antibody linker comprises a sequenceaccording to SEQ ID No. 3, or a sequence having at least 90% identity tothe sequence according to SEQ. ID. No. 3.

The antibody-part specifically binding to EDb-fibronectin is fused toInterleukin-2. Both parts may be fused directly, or may be fused via alinker, in particular by a peptidic fusion protein linker. Preferably,the fusion protein linker has a length of 1 to 30 amino acids. In aparticularly preferred embodiment, the fusion protein linker comprises asequence according to SEQ ID No. 5.

In another particularly preferred embodiment, the Interleukin-2 is humanInterleukin-2 (human IL-2).

Interleukin-2 may be produced recombinantly or may be isolated fromhuman tissue, preferably it is produced recombinantly (rIL-2). In anespecially preferred embodiment, the Interleukin-2 part comprises asequence according to SEQ. ID. No. 4, or a functional variant thereof.

The fusion protein may be monomeric, or multimeric, e.g. dimeric.Dimeric or other multimeric forms may be formed covalently ornon-covalently. E.g. L19(scFv)-IL2 may form non-covalent homodimers.

The fusion proteins are preferably produced recombinantly using methodsknown to the skilled person. In particular, prokaryotic or eukaryoticexpression systems, e.g. yeast or mammalian expression systems, can beused.

The combination of the present invention further comprises a moleculebinding to B cells, B cell progenitors and/or their cancerouscounterpart.

In one embodiment of the present invention, the molecule binding to Bcells, B cell progenitors and/or their cancerous counterpart islabelled, in particular radioactively labelled. Preferably, thelabelling is a covalent labelling.

In an especially preferred embodiment, the labelled molecule binding toB cells, B cell progenitors and/or their cancerous counterpart, is aradioactively labelled anti-CD20 antibody. Various radioactive labelsare used in medicine.

Particularly useful radioactive isotopes for labelling antibodies andproteins are ⁹⁰Y, ¹¹¹In and ¹³¹I-labelled. In an especially preferredembodiment, the anti-CD20 antibody is labelled with ⁹⁰Y, ¹¹¹In or ¹³¹I.

In a particularly preferred embodiment, the radioactively labeledanti-CD20 antibody is selected from Y-90-Ibritumomab-Tiuxetan(Y90-ZEVALIN® or -ZEVALIN®) and I-131 tositumomab (BEXXAR®).Y-90-Ibritumomab-Tiuxetan and its production is for example disclosed inEP 0 669 836 as Y2B8 (Yttrium-[90]-labeled 2B8-MX-DTPA).

In a preferred embodiment, the combination of the present inventionfurther comprises a molecule specifically binding to CD20. In anespecially preferred embodiment, this molecule is an antibody orantibody fragment, or a fusion protein thereof.

Particularly preferred are anti-CD20 antibodies which exhibit ADCCactivity.

In a further preferred embodiment, the anti-CD20 antibody is selectedfrom rituximab, Ocrelizumab, PRO131921, Veltuzumab, Ofatumumab, AME-133,and GA-101.

In a preferred embodiment of the invention, the antibodies specificallybinding to CD20 are in full IgG, Fab, (Fab)₂, scFv, diabody, minibody orsmall immunoprotein (SIP) format.

Also, the anti-CD20 antibody may be monomeric or multimeric, e.g.dimeric. Multimeric antibodies may be homomeric or heteromeric. E.g. abivalent antibody may be used, wherein one part specifically binds toCD20 and another part binds to another target. Also, the moleculespecifically binding to CD20 may comprise further effectors, inparticular it may be labelled radioactively. In this embodiment of thepresent invention, ZEVALIN® or BEXXAR® may be used, as described above.

A particularly preferred anti-CD20 antibody is rituximab, in particularRITUXAN® (also called MABTHERA® or IDEC-C2B8). RITUXAN® is a geneticallyengineered chimeric murine/human monoclonal antibody directed againstthe CD20 antigen found on the surface of normal and malignant Blymphocytes. The antibody is an IgG1 kappa immunoglobulin containingmurine light- and heavy-chain variable region sequences and humanconstant region sequences. rituximab is disclosed e.g. in U.S. Pat. No.5,843,439; 5,776,456 and 5,736,137.

In a more preferred embodiment, the combination comprises rituximab andL19-IL2.

In an even more preferred embodiment the L19 antibody is in scFv format.

Particularly preferred is L19-IL2 as described in Carnemolla et al.,Blood. 2002; 99:1659-1665.

Another embodiment of the present invention relates to a combination asdescribed above, for use as a medicament.

A further embodiment of the present invention relates to a combinationas described above, for use as a medicament for treating cancer.

In a preferred embodiment, the cancer is a lymphoma, preferably a B-celllymphoma. Most preferred is the use of the combination of the presentinvention for treating B-cell Non-Hodgkin lymphoma (B-NHL).

In a further preferred embodiment, the B-cell lymphoma is refractory orrelapsed B-cell lymphoma or a lymphoma resistant torituximab-monotherapy.

The invention further relates to a method of treating cancer, wherein acombination of the present invention is administered to a cancer patientin therapeutically effective amount. Preferably, the cancer is alymphoma, preferably a B-cell lymphoma, in particular a NHL.

A further embodiment of the present invention relates to a combinationas described above, for use as a medicament for treating autoimmunediseases, in particular chronic autoimmune diseases.

In a preferred embodiment, the autoimmune disease is rheumatoidarthritis, Crohn's disease, colitis ulcerosa or autoimmune hemolyticanemia.

The patient can be any mammal, preferably the patient is a human.

Various administration routes are possible, e.g. intravenous,subcutaneous or intraperitoneal administration, wherein the intravenousadministration is preferred.

Also, the fusion protein specifically recognizing EDb fibronectin andthe molecule binding to B cells, B cell progenitors and/or theircancerous counterpart may be administered at the same time or atdifferent time points. Moreover, the combination may be administeredonce or several times to a patient. Also, it is possible, that onecomponent of the combination is administered once, and the othercomponent is administered several times.

Typically, if rituximab and L19-IL2 are administered as combinationtherapy, they may be administered to a patient at the same time point,as this allows easier administration schedules. For examples, rituximaband L19-IL2 both may be administered i.v. once or twice per day in timeintervals ranging from few days up to 3 months. Also, one or moretreatment rounds are possible.

Moreover, the amount administered may vary. For example, rituximab maybe administered in an amount of about 20 to 500 mg/m², preferably in anamount of about 100 to 400 mg/m², in particular of about 375 mg/m²rituximab per administration. Typically, rituximab is administered onDay 1 of a 2-, 3-, or 4-week treatment schedule with up to 6-8 treatmentcycles (remission induction), although other administration schedulesare possible.

Therapeutic formulations of the active agents used in accordance withthe present invention are prepared for storage by mixing an active agenthaving the desired degree of purity with optional pharmaceuticallyacceptable carriers, excipients or stabilizers (Remington'sPharmaceutical Sciences 16th edition, Osol, A. Ed. (1980)), in the formof lyophilized formulations or aqueous solutions.

Exemplary anti-CD20 antibody formulations are described in WO 98/56418.This publication describes a liquid multidose formulation comprising 40mg/mL rituximab, 25 mM acetate, 150 mM trehalose, 0.9% benzyl alcohol,0.02% polysorbate 20 at pH 5.0 that has a minimum shelf life of twoyears storage at 2-8° C. Another anti-CD20 formulation of interestcomprises 10 mg/mL rituximab in 9.0 mg/mL sodium chloride, 7.35 mg/mLsodium citrate dihydrate, 0.7 mg/mL polysorbate 80, and Sterile Waterfor Injection, pH 6.5. Lyophilized formulations adapted for subcutaneousadministration are described in WO 97/04801. Such lyophilizedformulations may be reconstituted with a suitable diluent to a highprotein concentration and the reconstituted formulation may beadministered subcutaneously to the patient to be treated herein.

Also, for the fusion protein the amount to be administered may vary.Typically, the amount of L19-IL2 to be administered per administrationis about 1 to 10×10⁶ IU/m², in particular about 5 to 50×10⁶ IU/m²,especially about 10 to 30×10⁶ IU/m².

It is also possible that the administered amount varies over time; e.g.the amount of rituximab and/or L19-IL2 may be increased or decreased forone or more administration rounds.

Also, a maintenance treatment, in particular with rituximab or L19-IL2alone, may follow the combination treatment phase.

Also, it is possible to support with L19-IL2 the treatment withantibody-containing combination therapies against B-NHL, in particular,chemoimmunotherapeutic regimens (e.g. R-CHOP).

Antibody linker is any linker, preferably a peptide linker, which issuitable for linking Vh and Vl domains. Suitable linkers are for exampledescribed in Bird et al, Science, 242, 423-426, 1988; Huston et al, PNASUSA, 85, 5879-5883, 1988, EP 0 573 551; EP 0 623679 and EP 0 318554,which documents are introduced by reference.

Fusion protein linkers are linkers suitable for linking an antibody orantibody-fragment and a second biologically active protein, preferablythe linker is peptidic. Suitable linkers are described in EP 0 573 551;EP 0 623679 and EP 0 318554, which documents are introduced byreference. In particular, suitable linkers are described in EP 0 623679.

“Specifically binding” or “specifically recognizing” as used hereinrefers to binding to the corresponding target. Typically, the bindingmolecule, antibody, antibody fragment or antibody mimetic binds with anaffinity of at least about 1×10⁻⁷ M, preferably of at least about 1×10⁻⁹M, and binds to the predetermined target with an affinity that is atleast two-fold greater than its affinity for binding to a non-specifictarget (e.g. BSA, casein) other than the predetermined target or aclosely-related target.

“Antibody” as used herein encompasses full length antibodies, comprisingnative antibodies, monoclonal antibodies, polyclonal antibodies andmultispecific antibodies (e.g., bispecific antibodies), humanantibodies, humanized antibodies, chimeric antibodies, and full IgGantibodies, as well as antibody fragments.

The term “antibody fragment” refers to a portion of a full lengthantibody, in which a variable region or a functional capability isretained, namely the specific binding to the target. Examples ofantibody fragments include, but are not limited to, a Fab, Fab′,F(ab′)2, Fd, Fv, scFv and scFv-Fc fragment, a diabody, a linearantibody, small immunoprotein formats, a single-chain antibody, aminibody, a diabody formed from antibody fragments, and multispecificantibodies formed from antibody fragments. Antibody fragments areusually smaller than full antibodies. Thereby, the pharmacokinetics aredifferent and some antibody fragments only consist of one polypeptidechain, which can make production easier. However, such fusion proteinscomprising antibody fragments often suffer from a reduced stability.Preferably, the antibody fragment is in scFv, (scFv)2, or smallimmunoprotein format. The small immunoprotein format can be a formatbased on a CH3-domain (for example described in U.S. Pat. No. 5,837,821)or εS₂CH4-domain of human IgE (for example described in WO 03/076469).

The term “monoclonal antibody” (mAb) refers to an antibody obtained froma population of substantially homogeneous antibodies; that is, theindividual antibodies comprising the population that are identicalexcept for naturally occurring mutations that may be present in minoramounts. Monoclonal antibodies are highly specific, being directedagainst a single antigenic determinant, also referred to as an epitope.The modifier “monoclonal” is indicative of a substantially homogeneouspopulation of antibodies directed to the identical epitope and is not tobe construed as requiring production of the antibody by any particularmethod. Monoclonal antibodies can be made by any technique ormethodology known in the art; for example, the hybridoma method firstdescribed by Koehler et al., 1975, Nature 256:495, or recombinant DNAmethods known in the art (see, e.g., U.S. Pat. No. 4,816,567). Inanother example, monoclonal antibodies can also be isolated from phageantibody libraries, using techniques described in Clackson et al., 1991,Nature 352: 624-628, and Marks et al., 1991, J. Mol. Biol. 222: 581-597.

In contrast, the antibodies in a preparation of polyclonal antibodiesare typically a heterogeneous population of immunoglobulin isotypesand/or classes and also exhibit a variety of epitope specificity.

The term “chimeric” antibody as used herein is a type of monoclonalantibody in which a portion of or the complete amino acid sequence inone or more regions or domains of the heavy and/or light chain isidentical with, homologous to, or a variant of the correspondingsequence in a monoclonal antibody from another species or belonging toanother immunoglobulin class or isotype, or from a consensus sequence.

Certain types of antibody fragments can be generated by enzymatictreatment of a full-length antibody. Papain digestion of antibodiesproduces two identical antigen-binding fragments called “Fab” fragments,each with a single antigen-binding site, and a residual “Fc” fragment,so called because of its ability to crystallize readily. The Fabfragment also contains the constant domain of the light chain and theCH1 domain of the heavy chain. Pepsin treatment yields a F(ab′)2fragment that has two antigen-binding sites and is still capable ofcross-linking antigen.

Fab′ fragments differ from Fab fragments by the presence of a fewadditional residues at the C-terminus of the CH1 domain, including oneor more cysteines from the antibody hinge region. Fab-SH is thedesignation herein for a Fab′ in which the cysteine residue(s) of theconstant domains bear a free thiol group. F(ab′)2 antibody fragments arepairs of Fab′ fragments linked by cysteine residues in the hinge region.Other chemical couplings of antibody fragments are also known.

“Fv” is a minimum antibody fragment that contains a completeantigen-recognition and binding site consisting of a dimer of one heavyand one light chain variable domain in tight, non-covalent association.In this configuration, the three CDRs of each variable domain interactto define an antigen-binding site on the surface of the VH VL dimer.Collectively, the six CDRs confer antigen-binding specificity to theantibody.

A “single-chain Fv” or “scFv” antibody fragment is a single chain Fvvariant comprising the VH and VL domains of an antibody, in which thedomains are present in a single polypeptide chain and which is capableof recognizing and binding antigen. The scFv polypeptide optionallycontains a polypeptide linker positioned between the VH and VL domainsthat enables the scFv to form a desired three-dimensional structure forantigen binding (see, e.g., Pluckthun, 1994, In The Pharmacology ofMonoclonal Antibodies, Vol. 113, Rosenburg and Moore eds.,Springer-Verlag, New York, pp. 269-315).

The term “diabodies” refers to small antibody fragments having twoantigen-binding sites. Each fragment contains a heavy chain variabledomain (VH) concatenated to a light chain variable domain (VL). By usinga linker that is too short to allow pairing between the two domains onthe same chain, the linked VH-VL domains are forced to pair withcomplementary domains of another chain, creating two antigen-bindingsites.

Diabodies are described more fully, for example, in EP 404,097; WO93/11161; and Hollinger et al., 1993, Proc. Nat. Acad. Sc. USA 90:6444-6448.

A humanized antibody or a humanized antibody fragment includes animmunoglobulin amino acid sequence variant, or fragment thereof, whichis capable of binding to a predetermined antigen and which, comprisesone or more framework regions (FRs) having substantially the amino acidsequence of a human immunoglobulin and one or more CDRs havingsubstantially the amino acid sequence of a non-human immunoglobulin.This non-human amino acid sequence is referred to herein as an “import”sequence, which is typically taken from an “import” antibody domain,particularly a variable domain. In general, a humanized antibodyincludes at least the CDRs or HVLs of a non-human antibody, insertedbetween the FRs of a human heavy or light chain variable domain.

“Native antibodies” are defined herein as heterotetramericglycoproteins, typically of about 150,000 daltons, composed of twoidentical light (L) chains and two identical heavy (H) chains. Eachlight chain is covalently linked to a heavy chain by one disulfide bondto form a heterodimer. The heterotetramer is formed by covalentdisulfide linkage between the two identical heavy chains of suchheterodimers. Although the light and heavy chains are linked together byone disulfide bond, the number of disulfide linkages between the twoheavy chains varies by immunoglobulin isotype. Each heavy and lightchain also has regularly spaced intrachain disulfide bridges. Each heavychain has at the amino-terminus a variable domain (VH), followed bythree or four constant domains (CH1, CH2, CH3, and CH4), as well as ahinge region between CH1 and CH2. Each light chain has two domains, anamino-terminal variable domain (VL) and a carboxy-terminal constantdomain (CL). The VL domain associates non-covalently with the VH domain,whereas the CL domain is commonly covalently linked to the CH1 domainvia a disulfide bond. Particular amino acid residues are believed toform an interface between the light and heavy chain variable domains(Chothia et al., 1985, J. Mol. Biol. 186:651-663.) The term“hypervariable” refers to the fact that certain sequences within thevariable domains differ extensively in sequence among antibodies andcontain residues that are directly involved in the binding andspecificity of each particular antibody for its specific antigenicdeterminant. Hypervariability, both in the light chain and the heavychain variable domains, is concentrated in three segments known ascomplementarity determining regions (CDRs) or hypervariable loops(HVLs). CDRs are defined by sequence comparison in Kabat et al., 1991,In: Sequences of Proteins of Immunological Interest, 5th Ed. PublicHealth Service, National Institutes of Health, Bethesda, Md., whereasHVLs are structurally defined according to the three-dimensionalstructure of the variable domain, as described by Chothia and Lesk,1987, J. Mol. Biol. 196: 901-917.

Where these two methods result in slightly different identifications ofa CDR, the structural definition is preferred. As defined by Kabat,CDR-L1 is positioned at about residues 24-34, CDR-L2, at about residues50-56, and CDR-L3, at about residues 89-97 in the light chain variabledomain; CDR-H1 is positioned at about residues 31-35, CDR-H2 at aboutresidues 50-65, and CDR-H3 at about residues 95-102 in the heavy chainvariable domain.

The term “label” refers to a detectable compound or composition that isconjugated directly or indirectly to the antibody. The label may itselfbe detectable (e.g., radioisotope labels or fluorescent labels) or, inthe case of an enzymatic label, may catalyze chemical alteration of asubstrate compound or composition that is detectable.

Although fibronectins (FNs) are the product of the single FN gene, theresulting protein can exist in multiple forms which—apart fromposttranslational modifications—arise from alternative splicing of itsprimary RNA transcript. This polymorphism which leads to as many as 20different isoforms in human FN, thereby generating FNs with differentsolubility, cell adhesive and ligand-binding properties, provides cellswith the possibility to modify the composition of the extracellularmatrix (ECM) in a tissue-specific manner. Alternative splicing takesplace in three regions of the primary RNA transcript: Exon usage orskipping leads to either inclusion or omission of two type-III repeats,extra-domain B (EDB or ED-B, also termed EIIIB or EDIII), which isinserted between FN type-III repeats III7 and III8, or/and extra-domainA (EDA, also termed EIIIA or EDI), inserted between FN type-III repeatsIII11 and III12. This type of splicing occurs in many vertebrates,including Xenopus, chicken, rat, dog and human.

“ED-B domain” is to be understood as the extra-domain B of humanfibronectin. It is often referred to as EDb, EIIIB or EDII.

“Antibody mimetics” are understood as binding molecules based on proteinframeworks (“scaffolds”) which specifically bind to the target and whichare distinct from antibodies and antibody fragments. Such scaffolds aredescribed in Binz et al., 2005, Nat. Biotechnol. 23, 1257-1268. Antibodymimetics specifically binding to ED-B fibronectin are described inGrabulovski et al., J. Biol. Chem., 2007, 282:3196-3204.

“Interleukin-2” according to the present invention refers to mammalianInterleukin-2, preferably human Interleukin-2 and functional variantsthereof. Functional variants of Interleukin-2 are variants of humanInterleukin-2 which exhibit at least 10%, but more preferably more than50%, and even more preferred more than 90% of the activity of nativehuman Interleukin-2. Interleukin-2 activities are activities ofInter-leukin-2 in biochemical assays or in vivo, in particularInterleukin-2 activity can be measured by the effect on proliferationand/or differentiation of activated T and B lymphocytes and of naturalkiller cells and/or induction of cytotoxic T cell activity and/orNK/lymphokine activated killer (LAK) anti-tumour activity (Meazza R,Marciano S, Sforzini S, et al. Analysis of IL-2 receptor expression andof the biological effects of IL-2 gene transfection in small-cell lungcancer. Br. J. Cancer. 1996; 74: 788-795). In particular, functionalvariants are cystein-125 muteins of Interleukin-2 as described in EP0109748 and other muteins, including cystein muteins as described inEP136489, in particular serine 125-Interleukin-2. Also, the N-terminusof hIL.2 variants may be altered without significantly affecting theactivity, in particular the N-terminal 1-5 amino acids, especiallypreferred the N-terminal Alanine may be deleted or altered, preferablydeleted. Moreover, the Interleukin-2 may contain altered or deletedpost-translational modifications, in particular the glycosylationpattern may be altered or missing. Different or absent glycosylation maybe obtained e.g. either by mutating the sequence or by expression of thefusion protein in an appropriate host. For example, Aldesleukin, whichis approved for metastatic RCC, is unglycosylated des-alanyl-1,serine-125 human interleukine-2 produced in E. coli.

FIGURE LEGEND

FIG. 1. Immunohistochemistry with L19 antibody reveals EDB expression inB-cell lymphoma xenografts. Immunohistochemical staining using theantibody L19, specific to EDB fibronectin, revealed a strong expressionof this fibronectin isoform with a prominent vascular pattern ofstaining in Ramos lymphoma xenografts (left panel). The staining issimilar to the staining pattern of L19 in solid tumors, as exemplifiedwith the U87 glioblastoma xenograft (right panel). For negative control,the primary antibody was omitted. Scale bars, 100 μm.

FIG. 2. In vivo localization experiments: ex vivo immunofluorescence (A)and quantitative biodistribution studies (B). The in vivo targetingperformance of the L19 antibody was tested in the subcutaneousSCID/Ramos lymphoma model. (A) Lymphoma-bearing mice were injected withL19-SIP, chemically labeled with the fluorophore Cy3. The figure shows a2-color fluorescence microscopic image of a lymphoma section 241 h afterinjection, confirming the antibody localization (red) on tumor vascularstructures. An anti-CD31 antibody has been applied ex vivo to outlineendothelial cells and was detected with an Alexa Fluor 488 anti-rat IgGantibody (green). Scale bars, 100 μm. (B) Quantitative biodistributionresults were obtained 24 h and 48 h after injection of ¹²⁵I-radiolabeledL19-SIP into lymphoma-bearing animals (n≧3 for each time point). Meantargeting results are expressed as percent injected dose per gram oftissue (% ID/g±SD). Forty-eight hours after injection, a selectiveaccumulation and retention of the antibody in the lymphoma tissue couldbe observed, with tumor-to-blood ratios of 4.8 and tumor-to-organsratios ranging from 3.8 to 17.3.

FIG. 3. Effect of single-agent L19-IL2, unconjugated IL-2 and rituximabon lymphoma growth. SCID mice bearing established s.c. Ramos lymphomaxenografts were injected i.v. with either the vascular targeting L19-IL2fusion protein (▪; 20 μg), the corresponding dose of untargeted rIL-2(▴; 6.6 μg), rituximab (●; 200 μg), or control saline (X) on days 8, 11,14, and 17 after tumor cell implantation. Single-agent L19-IL2 andsingle-agent rituximab both delayed tumor growth significantly (P=0.024and P=0.004, respectively). In contrast, unconjugated rIL-2 did notexhibit significant therapeutic activity (P=0.383), indicating thecontribution of the targeted delivery of IL-2 to the therapeutic effect(L19-IL2 vs. IL-2: P=0.044).

FIG. 4. Therapeutic effect of L19-IL2 and unconjugated IL-2 incombination with rituximab. SCID mice bearing established s.c. lymphomaxenografts were injected i.v. with either saline (X), 200 μgrituximab+low dose unconjugated IL-2 (Δ; 2.2 μg), 200 μg rituximab+highdose unconjugated IL-2 (▴; 6.6 μg), 200 μg rituximab+low dose L19-IL2(□; 6.6 μg, corresponding to 2.2 μg IL-2), or 200 μg rituximab+high doseL19-IL2 (▪; 20 μg, corresponding to 6.6 μg IL-2) on days 8, 11, 14, and17. L19-IL2 in combination with rituximab was highly efficacious,inducing complete remissions in 4 of 5 mice in the low dose as well asin the high dose L19-IL2 group. In contrast, unconjugated rIL-2 incombination with rituximab did not induce tumor regressions and alltumors continued to grow. All mice with CRs remained tumor-free for aperiod of at least 42 days.

FIG. 5. Therapeutic effect of L19-IL2, IL-2 and rituximab in mono- andcombination therapies in the disseminated lymphoma model. SCID mice(n≧6) were injected i.v. with 2×10⁶ Ramos lymphoma cells and treated 8days later according to the following regimens: untargeted IL-2 (6.6μg), L19-IL2 (20 μg), rituximab (200 μg), rituximab (200 μg)+IL-2 (6.6μg), rituximab (200 μg)+L19-IL2 (20 μg), or control saline (In detail,to model systemic disease, SCID mice were injected i.v. with 2×10⁶ Ramoslymphoma cells resuspended in 200 μL PBS. Dissemination and growth ofB-cell lymphoma was allowed to occur for 8 days before the initiation oftherapy. Mice were randomly divided into 6 groups (≧6 mice per group)and injected i.v. with either saline, 20 μg L19-IL2, 6.6 μg unconjugatedrIL-2, or 200 μg rituximab (single-agent treatment groups), or 200 μgrituximab in combination with 20 μL19-IL2, or 200 μg rituximab incombination with 6.6 μg unconjugated rIL-2 (combination treatmentgroups), on days 8, 11, 14, and 17 (Q3Dx4). Mice were monitored dailyfor the presence of hind-leg paralysis or signs of a deterioratingcondition whereupon mice were sacrificed and scored as dead. Survivalwas recorded for analysis of therapeutic efficacy).

FIG. 6. Target validation in human lymphoma samples. EDB was found to beexpressed in neovascular structures of human B-cell lymphoma entities,including the frequent subtypes diffuse large B-cell lymphoma andBurkitt lymphoma. Scale bars, 100 μm.

FIG. 7. While the fusion protein L19-IL2 reproducibly inhibited lymphomagrowth (P=0.031), equimolar amounts of naked L19 in SIP or IgG formatwere therapeutically inactive when administered alone or in combinationwith free rIL-2.

EXAMPLES Materials and Method

Animals and Cell Lines

Six- to 8-week-old female CB17/lcr SCID mice were obtained from CharlesRiver Laboratories (Sulzfeld, Germany). All mice were housed inmicroisolator units and provided with sterile food and water ad libitumthroughout the studies. The EBV-negative human B cell lymphoma cell lineRamos⁴⁴ was purchased from the American Type Culture Collection (ATCC,Manassas, Va.). Cells were maintained in log-phase growth in RPMI 1640medium adjusted to contain 2 mM L-glutamine, 10 mM HEPES, 1 mM sodiumpyruvate, 4.5 g/L glucose, 1.5 g/L bicarbonate, 10% heat-inactivatedfetal bovine serum, 100 U/mL penicillin, and 100 μg/mL streptomycin. Thehuman follicular lymphoma cell line DoHH-2 was obtained from the GermanResource Centre for Biological Material (DSMZ, Braunschweig, Germany).

Antibodies and Reagents

L19 is a vascular targeting antibody directed against the EDB domain offibronectin. The expression, purification and characterization of L19 inSIP format (small immunoprotein) and the L19-IL2 fusion protein havebeen described previously in Borsi et al. (Int J. Cancer.2002;102:75-85) and Carnemolla et al. (Blood. 2002;99:1659-1665).Recombinant human IL-2 (Proleukin, 18×10⁶ IU) was obtained from ProreroPharma (Liestal, Switzerland) and the chimeric human IgG1 anti-CD20monoclonal antibody rituximab (MABTHERA®) from Roche (Reinach,Switzerland).

Immunohistochemistry

For immunohistochemistry on Ramos xenograft tumors, 10 μm cryostatsections of frozen samples were fixed in ice-cold acetone, rehydrated inTBS (50 mmol/L Tris, 100 mmol/L NaCl pH 7.4), and blocked with 20% FCS(Invitrogen, Basel, Switzerland). L19-SIP was added onto the sections ina final concentration of 10 μg/mL. Bound primary antibody was detectedwith rabbit anti-human IgE antibody (Dako, Glostrup, Denmark) followedby biotinylated goat anti-rabbit IgG antibody (Biospa, Milan, Italy) andstreptavidin-alkaline phosphatase complex (Biospa). Fast Red TRSalt(Sigma) was used as the phosphatase substrate. Immunohistochemicalanalysis of EDB expression in human lymphoma samples was performed usingbiotinylated L19-SIP and streptavidin-alkaline phosphatase (SAP).Sections were counterstained with hematoxylin, mounted with Glycergelmounting medium (Dako) and analyzed with an Axiovert S100 TV microscope(Zeiss, Feldbach, Switzerland).

Immunohistochemistry on human lymphoma samples was performed as onlymphoma xenografts, however, biotinylated L19-SIP was used as primaryantibody and detected with steptavidin-alkaline phosphatase complex(Biospa).

Ex Vivo Fluorescence Experiments

L19-SIP was labeled with Cy3-NHS ester, a fluorescent cyanine compound,following the manufacturer's recommendation (Amersham Pharmacia,Dübendorf, Switzerland). 120 μg of L19-Cy3 conjugate were injectedintravenously (i.v.) into the lateral tail vein of lymphoma-bearingmice. Mice were sacrificed 24 h after injection, and tumors wereexcised, embedded in cryoembedding compound (Microm, Walldorf, Germany)and stored at −80° C. 10 μm sections were cut, dried at 37° C. for 15min and fixed with 4% paraformaldehyde for 15 min at room temperature.Rat anti-CD31 antibody (BD Pharmingen) was applied to outlineendothelial cells using Alexa Fluor 488 rabbit anti-rat IgG as secondaryantibody (Invitrogen). Images were captured on an Axioskop 2 Mot plusmicroscope equipped with an AxioCam MRc camera (Zeiss).

Quantitative Biodistribution

To evaluate the in vivo targeting performance quantitatively,biodistribution analyses using radiolabeled antibody preparations wereperformed as described before (Camemolla et al., 2002). Briefly,purified SIP(L19) was radioiodinated with 1251 and injected i.v. intoSCID mice bearing s.c. implanted Ramos lymphoma xenografts or intoBalb/c mice bearing systemic syngeneic A20 lymphomas (10 μg, 12.2 μCiper mouse). Mice were sacrificed either 24 h or 48 h after injection, atleast three animals were used for each time point. Organs were weighedand radioactivity was counted using a Cobra γ counter (Packard, Meriden,Conn.). Radioactivity content of representative organs was expressed asthe percentage of the injected dose per gram of tissue (% ID/g±SE).

Localized Lymphoma Xenograft Model

1×10⁷ Ramos lymphoma cells or DoHH-2 (1×10⁷) lymphoma were injected s.c.into the flank of 6- to 8-week-old female CB17/lcr SCID mice on day 0.When tumors were established and clearly palpable (50-100 mm³, day 8after injection), mice were staged to maximize uniformity among thegroups and injected into the lateral tail vein with either 20 μL19-IL2(corresponding to 6.6 μg or 118000 IU rIL-2), 6.6 μg untargeted rIL-2,200 μg rituximab, or control saline in a volume of 100 μL on days 8, 11,14 and 17 (Q3Dx4). For combination therapy studies, L19-IL2 (6.6 and 20μg, corresponding to 2.2 and 6.6 μg of “free” rIL-2, respectively), orunconjugated rIL-2 (2.2 and 6.6 μg) were administered in combinationwith rituximab (200 μg) by separate i.v. injections on days 8, 11, 14,and 17. To test whether the L19 antibody alone was therapeuticallyactive, mice were treated with equimolar amounts of L19 in SIP (x.x μg)or IgG (x.x μg) format, alone or in combination with free rIL-2 (6.6μg). Treatment schedule for all agents (in mono- and combinationtherapies) was every third day for four (Ramos) or three (DoHH-2)injections in total (Q3Dx4 or Q3Dx3, respectively).

Mice were monitored daily and tumor growth was measured at least 3 timesper week with a digital caliper using the following formula:volume=length×width²×0.5. Responses were defined as complete remission(CR, no visible tumor) or partial remission (PR, at least 50% reductionof tumor volume). Animals were sacrificed when the tumor reached avolume>2000 mm³ or animals displayed signs of disease. All animalexperiments were done under the project license “Tumor Targeting” issuedto D. N. by the Kantonales Veterinäramt des Kantons Zürich (Bewilligung198/2005).

Disseminated Lymphoma Xenograft Model

To model systemic disease, SCID mice were injected i.v. with 2×10⁶ Ramoslymphoma cells resuspended in 200 μL PBS. Dissemination and growth ofB-cell lymphoma was allowed to occur for 8 days before the initiation oftherapy. Mice were randomly divided into 6 groups (n≧6) and injectedi.v. with either 20 μL19-IL2, 6.6 μg unconjugated rIL-2, or 200 μgrituximab (monotherapies), or 200 μg rituximab in combination with 20μL19-IL2, 200 μg rituximab in combination with 6.6 μg unconjugated IL-2(combination therapies), or saline on days 8, 11, 14, and 17 (Q3Dx4).Mice were monitored daily for the presence of hind-leg paralysis orsigns of a deteriorating condition whereupon mice were sacrificed. Onsetof paralysis or death were set as end points and survival of mice wasrecorded for analysis of therapeutic efficacy. Animal experiments usingthe disseminated lymphoma model were done in accordance with amendment 1to the project license “Tumor Targeting”.

Statistical Analysis

Data are expressed as the mean±SE. Differences in tumor volume betweendifferent groups of mice were compared using the two-tailed Student's ttest. Kaplan-Meier survival curves were performed to display therapeuticefficacy in the disseminated lymphoma model and comparisons were madeusing the log-rank test. Two-sided P values <0.05 were consideredsignificant.

Results

In Vitro Localization: Immunohistochemistry on Xenograft Tumors

Immunohistochemical analyses on sections of Ramos lymphoma xenograftshave been performed using L19 antibody specific to the EDB domain offibronectin). As demonstrated in FIG. 1 (left panel), a specificstaining of vascular structures in the lymphoma tissue could be observedfor L19, reminiscent of its staining pattern in solid tumors, asexemplified with a human U87 glioblastoma xenograft (right panel). Thepattern of EDB expression in lymphoma xenografts indicates that thisisoform can serve as target for the selective delivery of bioactivecompounds to the lymphoma site in vivo.

In Vivo Targeting Performance: Ex Vivo Fluorescence and QuantitativeBiodistribution

In the next step it was investigated whether EDB fibronectin expressedin lymphoma xenografts is accessible for the L19 antibody from thebloodstream in vivo. To this end, mice beating subcutaneous Ramoslymphoma tumors were injected i.v. with L19-SIP, chemically labeled withthe fluorophore Cy3. After 24 h, animals were sacrificed and tumorsections were processed as described in Materials and Methods, FIG. 2 ashows a 2-color fluorescence microscopic image of a lymphoma section,confirming the antibody localization on tumor vascular structures.

In order to evaluate antibody deposition quantitatively, mice bearings.c. implanted Ramos lymphoma xenografts were injected i.v. withradioiodinated preparations of L19-SIP. As depicted in FIG. 2 b, L19displayed an accumulation in the lymphoma tissue with absolute tumoruptake values of 4.7% ID/g 24 h after injection, but only moderatetumor-to-blood ratios of 2.1 at this time point (tumor-to-organ ratiosranging from 2.7 to 7.1). However, after 48 h, the antibody was clearedfrom normal organs more rapidly, resulting in increased tumor-to-blood(4.8) and tumor-to-organ ratios (up to 17.3) and demonstrating aspecific accumulation and retention of the antibody at the tumor site.

Therapeutic Activity of Single-Agent L19-IL2 and Single-Agent RituximabAgainst Localized Lymphoma Xenografts

It has been shown previously that the antibody-cytokine fusion proteinL19-IL2 exhibited potent anti-cancer activity in various models of solidtumors (Menrad et al. (Expert Opin Ther Targets. 2005; 9:491-500),Carnemolla et al. (Blood. 2002; 99:1659-1665)). To evaluate themonotherapeutic efficacy of L19-IL2 in B-cell lymphoma, SCID mice wereinjected s.c. with 1×10⁷ Ramos cells. On day 8 after tumor cellimplantation, when tumors had reached 50-100 mm³ in size, mice (n≧4)were treated i.v. either with 20 μL19-IL2 (corresponding to 6.6 μgrIL-2), 6.6 μg unconjugated rIL-2, 200 μg rituximab, or saline (Q3Dx4).FIG. 3 demonstrates that single-agent L19-IL2 and single-agent rituximabsubstantially inhibited lymphoma growth as compared to control micetreated with saline (P=0.024 and P=0.004, respectively). By contrast,equimolar amounts of unconjugated rIL-2 did not exhibit any significanttherapeutic effect (P=0.383), similar to what has been reportedpreviously for animal models of solid cancers and demonstrating thecontribution of the antibody-mediated vascular targeting of the cytokineto the therapeutic effect (L19-IL2 vs. IL-2: P=0.044). However, bothL19-IL2 and rituximab only delayed tumor growth when used as monotherapyand all animals experienced progressive disease in this experiment.While the fusion protein L19-IL2 reproducibly inhibited lymphoma growth(P=0.031), equimolar amounts of naked L19 in SIP or IgG format weretherapeutically inactive when administered alone or in combination withfree rIL-2, further reinforcing the concept that the therapeuticactivity of L19-IL2 relied on the targeted delivery of the cytokine atthe lymphoma site (FIG. 7).

To provide information about treatment-associated toxicity, animalweights were measured at least 3 times per week. No evidence of toxicitywas observed, as in none of the therapy groups mice lost more than 3% ofbody weight throughout the study period.

Therapeutic Activity of L19-IL2 and Rituximab in Combination AgainstLocalized Lymphoma Xenografts

A variety of ways to enhance the clinical efficacy of rituximab havebeen reported, including the administration of rIL-2 to potentiateADCC-mediated killing of lymphoma cells (Cartron et al., Blood. 2004;104:2635-2642). Thus, we asked whether a combination ofvascular-targeted IL-2 and anti-CD20 therapy would be therapeuticallymore effective than either therapeutic approach alone and, inparticular, whether the antibody-mediated accumulation of IL-2 in thelymphoma tissue would exceed the efficacy of a combination of theunconjugated cytokine and rituximab. To this end, a combination therapyexperiment was conducted according to the following scheme (≧5 mice pergroup): 200 μg rituximab+2.2 μg unconjugated rIL-2 (“low dose”), 200 μgrituximab+6.6 μg unconjugated rIL-2 (“high dose”), 200 μg rituximab+6.6μL19-IL2 (“low dose”, corresponding to 2.2 μg rIL-2), 200 μgrituximab+20 μg L19-IL2 (“high dose”, corresponding to 6.6 μg rIL-2), orcontrol saline. In analogy to the monotherapy experiment, injectionswere started on day 8 after tumor cell inoculation when palpable s.c.xenografts have developed and repeated every third day for 4 injectionsin total.

As shown in FIG. 4, rituximab in combination with unconjugated rIL-2caused significant tumor growth delay as compared to controls(rIL-2_(low and high dose) vs. saline: P<0.001). High dose rIL-2 wasslightly more effective in increasing the efficacy of rituximab than lowdose rIL-2 (P=0.038), however, no tumor regressions have been observedand all tumors continued to grow. In contrast, the combination ofrituximab with the L19-IL2 fusion protein displayed a strikingly higheranti-lymphoma activity and induced complete eradications of establishedRamos lymphomas in 4 of 5 mice in the high dose L19-IL2 group(L19-IL2_(high dose) vs. saline: P<0.00001), with 3 of 4 CRs (completeremessions) already being achieved after 3 injections. In fact, theimmunocytokine was remarkably more potent than the correspondingequimolar amount of unconjugated rIL-2 in combination with rituximab(L19-IL2_(high dose) vs. rIL-2_(high dose): P<0.001). Notably, evenL19-IL2 at the lowest dose level combined with rituximab still displayedan excellent therapeutic activity (L19-IL2_(low dose) vs. saline:P<0.00001; L19-IL2_(low dose) vs. rIL-2_(low dose): P<0.00001), inducingCRs in 4 of 5 cases after 4 cycles of therapy, whereas even a three-foldhigher dose of the non-targeted cytokine combined with rituximab wasonly able to retard tumor growth (L19-IL2_(low dose) vs.rIL-2_(high dose): P<0.001). While animals having achieved a CR in thelow dose L19-IL2 group eventually relapsed after remission duration of21, 48, 50, and 81 days, respectively, all CRs in the higher doseL19-IL2 group were durable and all mice remained tumor-free for anobservation period of one year. Two mice (one in the low dose and one inthe high dose L19-IL2 group) did not achieve a CR but the tumor mass wasreduced to less than 20 mm³.

To investigate whether the therapeutic performance of L19-IL2, alone orin combination, could be reproduced in a second lymphoma model, SCIDmice bearing localized DoHH-2 follicular lymphoma xenografts weretreated with similar conditions as indicated above. In analogy to theRamos model, L19-IL2 was effective as a single-agent in inhibitinglymphoma growth (P<0.0001), yet without inducing tumor regressions,while the sum of its components (naked L19 and rIL-2) in equivalentdoses showed no significant therapeutic activity. When combined withrituximab, L19-IL2 reproducibly led to complete tumor eradications inall cases (5/5) with no evidence of relapse at day 41 and wassignificantly more effective than single-agent rituximab or thecombination of rituximab and non-targeted rIL-2 (and naked L19)(P<0.01), even though ⅖ CRs had been observed in both groups.

The therapeutic activity of all agents used against localized Ramos andDoHH-2 xenografts in mono- and combination therapies is summarized inTable 3.

Importantly, the therapeutic performance of the combination therapy wasnot associated with additional toxicity. Mice did not exhibitsignificant loss of body weight at any time point during the treatment(<3%), indicating that also the combination therapy regimens were welltolerated.

TABLE 1 Activity of rIL-2, L19-IL2 and rituximab, alone and incombination, against localized lymphoma xenografts Relapse Treatment PRCR after CR Ramos Saline 0/9 0/9 — rIL-2 (6.6 μg) 0/4 0/4 — L19-IL2 (20μg) 0/4 0/4 — Rituximab (200 μg) 0/4 0/4 — Rituximab (200 μg) + rIL-2(2.2 μg) 0/5 0/5 — Rituximab (200 μg) + rIL-2 (6.6 μg) 0/5 0/5 —Rituximab (200 μg) + L19-IL2 (6.6 μg) 1/5 4/5 4/4 Rituximab (200 μg) +L19-IL2 (20 μg) 1/5 4/5 0/4 DoHH-2 Saline 0/5 0/5 — rIL-2 (6.6 μg)[+SIP(L19)] 0/5 0/5 — L19-IL2 (20 μg) 0/5 0/5 — Rituximab (200 μg) 2/52/5 1/2 Rituximab (200 μg) + rIL-2 (6.6 μg) [+SIP(L19)] 3/5 2/5 1/2Rituximab (200 μg) + L19-IL2 (20 μg) 0/5 5/5 0/5 SCID mice bearingestablished subcutaneous Ramos or DoHH-2 lymphoma xenografts weretreated with the indicated therapeutic regimens. Responses were definedas partial remission (PR, at least 50% reduction of tumor volume) orcomplete remission (CR, no visible or palpable tumor). Data indicatenumber responding/total number of treatment group. — not applicable.Therapeutic Activity in the Disseminated Lymphoma Model

Therapeutic activity of L19-IL2 as a single-agent and in combinationwith rituximab against disseminated lymphoma xenografts

Advanced NHLs in humans commonly develop as disseminated disease. Toinvestigate the activity of L19-IL2 against systemic lymphoma, we chosethe disseminated SCID/Ramos lymphoma model. SCID mice inoculated i.v.with lymphoma cells regularly develop paralysis of the hind-legs,resulting from lymphoma manifestations in the spinal cord and indicatingthe terminal phase of the disease. In accordance to publishedobservations, i.v. injection of Ramos cells resulted in the developmentof hind-leg paralysis by day 26 in all cases in a pilot experiment,indicating an engraftment rate of 100% (data not shown). As paralysispreceded death in every case, the appearance of hind-leg paralysis wasset as end point for survival analyses. Treatment initiation was delayedfor 8 days to ensure engraftment and outgrowth of lymphoma cells. Dosingand scheduling of agents were identical to the ones used in thelocalized Ramos lymphoma model, and the activities of both mono-(rIL-2,L19-IL2, rituximab) and combination therapies (rituximab plus rIL-2,rituximab plus L19-IL2) were evaluated simultaneously in thisexperiment.

The Kaplan-Meier survival curve is shown in FIG. 5. By day 25, allsaline-treated control mice succumbed to disseminated disease with amedian survival time of 24 days. The administration of unconjugatedrIL-2 alone did not exhibit a significant therapeutic benefit (mediansurvival 24 days; P=0.518, log-rank test). In contrast, thecorresponding dose of single-agent L19-IL2 (20 μg) extended the mediansurvival time to 29 days (P<0.010, compared to non-targeted rIL-2) andwas equally efficient as rituximab in delaying the appearance of thedisease compared to saline-treated controls (median survival 29 and 30days, respectively, vs. 24 days; P<0.001 for both agents). Incombination therapies, the addition of rIL-2 to rituximab delayed theappearance of the disease only slightly compared to rituximab alone,without reaching statistical significance (34 vs. 30 days; P=0.180).Notably, while all mice treated with single-agent therapies as well asall mice treated with the combination of rituximab and non-targetedrIL-2 eventually developed terminal paralysis, 6 of 6 mice receivingL19-IL2 and rituximab in combination survived more than 60 days withoutshowing clinical manifestations of the disease. On day 62, one mouse hadto be killed because of weight loss and ocular discharge due toinfection, with no evidence of paralysis or lymphoma manifestations atnecropsy. Two additional mice had to be sacrificed on day 73 and 79,respectively, due to lymphoma development in an axillary lymph node, yetwithout hind-leg paralysis. The three remaining mice were stilldisease-free 310 days after tumor cell inoculation.

Validation of Target Expression in Human Lymphoma Samples

Finally, immunohistochemical analyses confirmed the presence andvascular expression pattern of EDB fibronectin in human B-cellmalignancies, including diffuse large B-cell and Burkitt lymphomas (FIG.6).

REFERENCES

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Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The preceding preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

In the foregoing and in the examples, all temperatures are set forthuncorrected in degrees Celsius and, all parts and percentages are byweight, unless otherwise indicated.

The entire disclosures of all applications, patents and publications,cited herein and of corresponding EP application No. 08075044.1, filedJan. 17, 2008, and U.S. Provisional Application Ser. No. 61/021,718,filed Jan. 17, 2008, are incorporated by reference herein.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

The invention claimed is:
 1. A combination comprising at least (i) afusion protein comprising two parts, wherein the first part is anantibody which specifically recognizes an extra domain B (ED_(b)) offibronectin, and the second part is an Interleukin-2 polypeptide whichcomprises the amino acid sequence set forth in SEQ ID NO: 4; and (ii)rituximab.
 2. A combination according to claim 1, wherein the antibodyand the Interleukin-2 of said fusion protein are linked by a fusionprotein linker.
 3. A combination according to claim 1, wherein theantibody of (i) recognizes the ED_(b) domain of fibronectin andspecifically binds thereto with sub-nanomolar or nanomolar affinity. 4.A combination according to claim 1, wherein the antibody comprisescomplementarity determining region (CDR) sequences comprising VH-CDR1-3sequences and VL-CDR1-3 sequences of the L19 antibody.
 5. A combinationaccording to claim 4, wherein the VH-CDR1-3 sequences are set forth inSEQ ID NO:6, SEQ ID NO:8 and SEQ ID NO:7, respectively; and theVL-CDR1-3 sequences are set forth in SEQ ID NO:9, SEQ ID NO:10 and SEQID NO:11.
 6. A combination according to claim 1, wherein the antibodycomprises at least one Variable heavy (VH) chain according to SEQ ID NO:1 or at least one Variable light (VL) chain according to SEQ ID NO: 2.7. A combination according to claim 1, wherein the antibody comprisesone VH (variable heavy) chain according to SEQ ID NO: 1 and one VL(variable light) chain according to SEQ ID NO:
 2. 8. A combinationaccording to claim 1, wherein the antibody comprises at least oneVariable heavy (VH) chain according to SEQ ID NO: 1 and at least oneVariable light (VL) chain according to SEQ ID NO: 2, wherein thevariable heavy chain and the variable light chain are connected by anantibody linker.
 9. A combination according to claim 8, wherein theantibody linker is a polypeptide comprising at least 90% sequenceidentity to the polypeptide sequence set forth in SEQ ID NO:
 3. 10. Acombination according to claim 1, wherein the antibody and theInterleukin-2 are connected by a fusion protein linker.
 11. Acombination according to claim 10, wherein the fusion protein linker hasa length of 1 to 30 amino acids.
 12. A combination according to claim10, wherein the fusion protein linker comprises the sequence set forthin SEQ ID NO:
 5. 13. A pharmaceutical composition which comprises acombination according to claim 1 and a carrier.
 14. A method for thetreatment of lymphoma in a subject in need thereof, comprisingadministering into said subject, the combination according to claim 1.15. A method according to claim 14, wherein the lymphoma is a B-celllymphoma.
 16. A method according to claim 15, wherein the B-celllymphoma is non-Hodgkin's lymphoma.
 17. A method for the treatment of anautoimmune disease in a subject in need thereof, comprisingadministering into said subject, the combination according to claim 1.18. A method according to claim 17, wherein the autoimmune disease isrheumatoid arthritis, Crohn's disease, colitis ulcerosa or autoimmunehemolytic anemia.